CMD_LIST RAM size for STM32N6

[Okeskin]

Hi All,

I'm currently developing a project using an STM32N655. I'm using a 1024x600 px screen. The image format is ARGB8888. Naturally, my frame buffer takes up approximately 2.5 MB. I needed to reduce the size of the CMD list.

My application doesn't have vector graphics or fonts. Can I reduce the size of the CMD list as much as I want? Will this affect performance?

Also, it's not possible to double flash with internal RAM while running a screen of this size. However, would creating frames of different sizes affect the FPS? Currently, the frame rate is 32ms.

Best Regards,

Onur

[JohanAstrup]

Hello @Okeskin.

Decreasing the size of the Nema command list may reduce performance. However, it is usually vector graphics that is heavily using the command list. If you are only doing blitting operations, I assume you could reduce it quite a lot without impacting performance. However, you would need to test yourself, as it depends on the specific application.

I’m not entirely sure what you mean by “creating frames of different sizes”. Could you please elaborate on that?

Also, are you currently using a single framebuffer in internal RAM, or a double framebuffer in external RAM?

Best regards,
Johan

[Okeskin]

Hi Johan,
I currently have a 1024x600 screen and I'm using 16-bit color (RGB565). I'm printing the camera data as a 600x480 resolution, also in RGB565 format, to the second layer. So touchgfx actually uses a single layer; the second layer is just for the camera.

You can see a video of the application I made. My RAM usage is approximately 3.5MB.

I've significantly reduced the CMD list. Honestly, it hasn't made a huge difference.

However, a new challenge awaits me. I currently need to scale the camera image to 1024x600. I want to know if this is a vector graphics process, meaning I'll need more RAM.

BR,

Onur

[JohanAstrup · Accepted solution]

To me, it is not entirely clear how you want to achieve this, or whether TouchGFX is involved in the scaling.

In general, no: this is not a vector-graphics operation; it is simply scaling from pixels to pixels.

If you are using TouchGFX to perform the upscaling, I would recommend using the camera buffer as a dynamic bitmap in TouchGFX, which can then be used with a TextureMapper or ScalableImage.

Best regards,
Johan